Lesson 8 - The Collections Java utility class - Getting and modifying

In the previous lesson, Queue and Stack in Java, we introduced the queue and the stack. In today's Java tutorial, we're going to focus on the Collections library class, which contains a large number of utility methods to simplify the work with collections.

The Collections Class

This class belongs to the java.util package. Its methods could be categorized into several categories:

• getting data from collections
• modifying existing collections
• creating new collections

Getting Data From Collections

We can use the following methods to get useful information from a collection:

disjoint()

This method returns true, if two given collections do not contain the same elements:

{JAVA_OOP}

import java.util.Collections;
import java.util.Collection;
import java.util.Arrays;

{JAVA_MAIN_BLOCK}
final Collection<String> c1 = Arrays.asList("Carl", "Paul", "Michael");
final Collection<String> c2 = Arrays.asList("John", "Jack", "Peter");
final boolean disjoint = Collections.disjoint(c1, c2);
System.out.println("Collections don't contain the same elements: " + disjoint);
{/JAVA_MAIN_BLOCK}
{/JAVA_OOP}

The result:

Console application
Collections don't contain the same elements: true

frequency()

Finds out

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